Rotary knives with ring-like power-driven blades of the type pertaining to this invention are exemplified by such structures as shown in U.S. Pat. No. Re. 25,947; U.S. Pat. Nos. 4,142,291; 4,166,317, and 4,175,321. Such knives have a rotary ring-like or annular blade, generally frusto-conical in form, sharpened at one axial end and incorporating gear teeth to form a ring gear portion at the other axial end. The ring gear portion is located and guided by a ring-like housing that is secured to a handpiece. The blade is driven by a pinion carried by the handpiece. A flexible cable driven by an external motor, or an air motor incorporated into the handpiece, drives the pinion.
In a construction such as that shown in U.S. Pat. No. Re. 25,947, a disc-like pinion cap secured to the handpiece covers the pinion and overlies a portion of the blade adjacent the gear teeth. A modified cap construction is disclosed and claimed in the above-mentioned copending application Ser. No. 485,738. In constructions such as those shown in the other above-referenced patents, an annular-like gauge member for controlling the depth of cut is secured to the handpiece and has a base portion that covers the pinion in place of the pinion cap and has sufficient height in the axial direction to allow relative adjustment of its position axially of the blade while covering the pinion.
The above-referred to constructions do not fully prevent particles of material being cut from traveling with the blade into the pinion area where they accumulate and interfere with pinion rotation and engagement of the pinion with the gear teeth of the blade. This necessitates disassembly and cleaning during use. In addition, with the gauge set to a position close to the blade, the base of the gauge blocks the path of movement of small scraps or the like that sometimes tend to be carried by the blade. Where the product is firm or hard fat, often chilled, for which knives of this construction are used, this creates no problem; but where wet or soft hams, which are either fresh or salt-cured and have sinew and unchilled fat, are to be trimmed, the scrap material is particularly troublesome and is apt to work behind the gauge or pinion cap through clearances between the housing, blade, and gauge or cap.